The present invention relates to a thermo reversible recording medium, member having information memorizing part, thermo reversible recording label, and a method of and apparatus for image pressing for forming of deleting images repeatedly by utilizing a thermo sensible layer manifesting reversible change between transparent and non-transparent condition depending on temperature.
Recently, attention has been given to a thermo reversible recording medium having a heat sensible layer of which transparency can be reversed based on temperature. When such a recording medium is used in display monitors, images can be repeatedly formed or deleted when desired.
As typical examples, there are known thermo reversible recording media obtained by dispersing an organic lower molecular weight substance such as a higher fatty acid and the like in a resin mother material such as a vinyl chloride-vinyl acetate copolymer. Such a medium is disclosed, for example, in Japanese Patent Application Laid-Open (JP-A) No. 55-154198.
However, in case of the above-mentioned thermo reversible recording medium the transparent-state temperature range in which transparency the medium achieves a transparent-state is as narrow as 2 to 4xc2x0 C. Thus, this medium has a drawback that the transparent-state temperature range is too narrow to stably record and erase images. In attempting to widen the transparent-state temperature range, higher fatty acid, higher ketone or fatty ester and an aliphatic dicarboxylic acid in admixture may be used as suggested in, for example, JP-A Nos. 2-1363, 3-2809, 4-366682 or 6-255247. Since the transparent-state temperature range becomes wider, the temperature control becomes easier.
The thermo reversible recording media are often used in, for example, point cards (a card given to a customer by a shopkeeper and in which points are added each time some service is used). Such point cards are used repeatedly over a long period of time. Such a card may be put in pant pocket, purse or in table drawer. In other words, the card is stored under various conditions or environments.
However, if basic substances such as ammonia, amine and the like exist where the card has been stored, there is a problem that an opaque image cannot be formed even if the amount of such substances is extremely small. The reason for this is supposed that a carboxyl group of the organic lower molecular weight substance reacts with the basic substance resulting in formation of salts thereof. Therefore, the melting point of the organic lower molecular weight substance increases.
JP-A No. 5-294062 suggests use of higher ketone or fatty ester and a saturated aliphatic bisamide in admixture to make the transparent-state temperature range wider. Since organic lower molecular weight substance having a carboxyl group is not used, the influence by the basic substance is small, the temperature is somewhat wider, and erasing property is better. However, there is a drawback that the contrast is low.
Further, JP-A No. 11-58988 suggests, to decrease influence by a basic substance, use of organic lower molecular weight substance having lower melting point such as fatty ester and fatty acid metal salt such as copper stearate, or fatty amide and the like. However, if copper stearate is used, there is a drawback that the medium becomes blue colored blue due to blue color of the raw material. Moreover, if fatty amide is used, since the melting point of the fatty amide is not so higher, there is a drawback that the transparent-state temperature range becomes narrower.
It is an object of the present invention to provide a thermo reversible recording medium which can provide sufficient opacity even if it is stored in the presence of a basic substance. It is another object of the present invention to provide a thermo reversible recording medium which has a wider transparent-state temperature range, by which high contrast images can be formed or images can be erased irrespective of changes in environmental temperature. It is another object of the present invention to provide a thermo reversible recording label, a member having an information memorizing part and a reversible display part, an image processing method and an image processing apparatus, to which a thermo reversible recording medium, solution means of the first and second objects, is applied.
The thermo reversible recording medium of one aspect of this invention comprises a substrate and a heat sensible layer. This thermo sensible layer is made of resin and organic lower molecular weight substance and can reversibly achieve transparent-state or opaque-state depending on temperature. The organic lower molecular weight substance is a linear hydrocarbon-containing compound having no carboxyl group. The organic lower molecular weight substance may be any one or more of (1) linear hydrocarbon-containing compounds having a urethane bond, (2) linear hydrocarbon-containing compounds having a sulfonyl bond, (3) linear hydrocarbon-containing compounds having an oxalic diamide bond, (4) linear hydrocarbon-containing compounds having a diacylhydrazide bond, (5) linear hydrocarbon-containing aliphatic compounds having a urea bond and urethane bond, (6) linear hydrocarbon-containing aliphatic compounds having a urea bond and amide bond, (7) linear hydrocarbon-containing aliphatic compounds having a plurality of urea bonds, (8) linear hydrocarbon-containing cyclic compounds having a urea bond, (9) linear hydrocarbon-containing cyclic compounds having an amide bond.
Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.